Eddy current modelling for ILC target

ILC meeting 31st Jan- 3rd Feb 2007

IHEP-Beijing

James Rochford

Modelling ILC target

Short talk on eddy current modelling of ILC disk

Outline:• Electra modelling of LLB rotating disk experiment

– To build confidence in Electra code

• Use Electra to model the ILC wheel

Rotating disk experiment

Used some optimiser code to develop a model of experimental permanent magnet

radius 6.34 mmdz/ 2(half) 14.91 mm

(T) (A/ m)0 -884309.87

0.223005 -707447.90.44601 -530585.92

0.669015 -353723.951.115025 0

final magnet dimensions

Fitted magnetic properties

0

0.2

0.4

0.6

0.8

1

1.2

-1000000 -800000 -600000 -400000 -200000 0

H (A/ m)

B (T

)

Typical NdFeBomagnet data(Sumitomomanufacturers datafor NdFeBo)fitted usingoptimisation code

6.34mm

29.82mm

Rotating disk experiment

A comparison of model and experimenal derived field values given for axial plot along th emagnet axis from the magnet face

-0.6

-0.5

-0.4

-0.3

-0.2

-0.1

0

0 2 4 6 8 10 12

Axial position from magnet face (mm)

Fie

ld (

T)

Experimental

Model

Final field match for experimental permanent magnet

A comparison of model and experimenal derived field values given for radial plots at different axia; positions w.r.t the

magnet face

-0.5

-0.45

-0.4

-0.35

-0.3

-0.25

-0.2

-0.15

-0.1

-0.05

0

0 5 10 15 20 25

Radial position from axis (mm)

Fie

ld (

T)

Data Z= 1 mm

Model z=1mm

Data Z= 9 mm

Model z=9mm

Good match to field data

Rotating disk experiment

Electra model of copper disk

Permament magnet ‘NdFeB’ properties defined from optimiser fit

Variable magnet gap

Conductor – initial model copper 1.68e-8Ωm

Rotating disk experiment

Eddy currents A/mm2 @2000rpmUnit vectors

Initial model results for gap 0.254mm

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

4.0

4.5

5.0

0 500 1000 1500 2000Rotation rate (rpm)

Axi

al for

ce (lb

f)

Experiment magnet gap 0.254mm

Model: mu=1 rho =1.69e-8 ohm.m, gap 0.254mm

Model: mu=1 rho =2.25e-8 ohm.m, gap 0.254mm

Rotating disk experiment

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

0 200 400 600 800 1000 1200 1400 1600 1800 2000

Rotation rate (rpm)Tor

que

(N.m

)

Experiment magnet gap 0.254mm

Model: mu=1 rho =1.69e-8 ohm.m,gap 0.254mmModel: mu=1 rho =2.25e-8 ohm.m,gap 0.254mm

•Conductivity of disk not measured blue curve - high cond copperRed curve 0.75 times high cond copper

Fit dependant of conductivity of copper used

Final model results for all gap spacing's

Rotating disk experiment

Models use 0.75 times conductivity of high cond copper

0.0

0.5

1.0

1.5

2.0

2.5

0 500 1000 1500 2000

Rotation rate (rpm)

Tan

gent

al fo

rce

(lbf

)

Experiment magnetgap 0.254mm

Model: mu=1 rho=2.25e-8 ohm.m, gap0.254mmExperiment magnetgap 1.27mm

Model: mu=1 rho=2.25e-8 ohm.m, gap1.27mmExperiment magnetgap 2.54mm

Model: mu=1 rho=2.25e-8 ohm.m, gap2.54mm

Final model results for all gap spacing's

Rotating disk experiment

Models use 0.75 times conductivity of high cond copper

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

4.0

0 500 1000 1500 2000

Rotation rate (rpm)

Axi

al fo

rce

(lbf

)

Experiment magnet gap0.254mm

Model: mu=1 rho =2.25e-8 ohm.m, gap 0.254mm

Experiment magnet gap1.27mm

Model: mu=1 rho =2.25e-8 ohm.m, gap 2.54mm

Experiment magnet gap2.54mm

Model: mu=1 rho =2.25e-8 ohm.m, gap 1.27mm

ILC wheel model

Wheel parametersWheel dia: 2m

Axial thickness: 14mmRadial thickness: 50mm

Material: Ti alloy

Focusing solenoidsUpstream:

Outer radius 540mmInner radius 225mmAxial length 250mm

Axial offset from wheel centre 100mm

Jden 46A/mm2

Downstream:Outer radius 400mmInner radius 225mmAxial length 50mm

Axial offset from wheel centre 100mm

Jden 46A/mm2

Ti alloy Ti6Al4V 1.08e-6Ωm

ILC wheel model

Field from focusing solenoids

Axis field Bz

ILC wheel model

Mesh distribution in wheel

Optimised to model eddy currents in

wheel

Will need to add higher mesh density

on coil axis to improve field

modelling here

ILC wheel model

Eddys @ 2000rpm

ILC wheel model

Power required to drive wheel @

different rotational speeds

Integrate power dissipation in wheel volume

directly in model –I2r

Model-torque calculated use this

to calc power provided by

braking force

Should be equivalent

Power to drive 2 meter ILC wheel

0

200

400

600

800

1000

1200

0 500 1000 1500 2000 2500 3000

Rotation rate

Pow

er d

issipa

ted

in ri

ng a

nd 'b

raki

ng fo

rce' (k

W)

.Power dissipated in eddy currents

Mechanical work done

The large power required to drive the wheel may pose a problem in the design.

ILC wheel model

Electra model of cu disk good agreement with expt

Started to model ILC wheel

How to proceed?

Need some directions here

Look at 1m wheel

Look at field effects on 2 m version

Modelling a pulsed system

…….?